Generally, any type of handlebar for a bicycle is made from a pipe round in section, so that turbulent air flow occurs at the rear of the handlebar in the forward moving direction of the bicycle when running at high speed, causing air resistance to running. The handlebar carries at one end or often at both ends control levers mainly for the brakes, or for a derailleur. Control wires and other sheaths guiding the wires, are connected to the levers and extend therefrom along the bicycle frame, such as a top tube or head pipe, to brakes at the front and rear wheels or to a derailluer. The wires and outer sheaths, in the vicinity of the lever, are bent at a larger curvature and forwardly project from the handlebar in opposition to a large air resistance to the bicycle's running. This is not preferred, especially for a racing bicycle used in a road race, and also gives the bicycle a poor appearance.
The former problem concerning the sectional shape of the handlebar can be solved by making a handlebar with a streamlined section, but the handlebar is complex to machine and expensive to produce in comparison with that formed from a round pipe. The latter problem of projecting wires and outer sheaths can be solved by inserting the control wires into the bar body, but through-bores are necessary, reducing the strength of the bar body. Hence, both the aforesaid problems cannot be solved.